Numerous surgical procedures have been developed to replace arteries that have become blocked by disease. The aortocoronary bypass surgery is perhaps the most important of these bypass operations. The coronary arteries supply blood to the heart. As a result of aging and disease, coronary arteries may become blocked by plaque deposits, stenosis, or cholesterol. In some instances, these blockages can be treated with artherectomy, angioplasty or stent placement, and coronary bypass surgery is not required. Coronary bypass surgery is required when these other methods of treatment cannot be used or have failed to clear the blocked artery. In the coronary bypass surgery, a vein is harvested from elsewhere in the body and grafted into place between the aorta and the coronary artery beyond the point of blockage.
The coronary bypass surgery requires a length of vein or artery for the graft. It is preferred to use a vein taken from the patient undergoing the bypass surgery. The patient is a ready source of suitable veins that will not be rejected by the body after transplantation and grafting onto the aorta and coronary artery. The saphenous vein in the leg is the best substitute for small arteries such as the coronary arteries, and it is the preferred vein for use in coronary bypass surgery. This is because the saphenous vein is typically 3 to 5 mm in diameter, about the same size as the coronary arteries. Also, the venous system of the legs is sufficiently redundant so that after removal of the saphenous vein, other veins that remain in the leg are adequate to provide adequate return blood flow. The cephalic vein in the arm is an alternative that is sometimes used.
In a typical operation previously required to harvest the saphenous vein, the surgeon cut into the leg to allow access to the saphenous vein and cut the vein from the leg. To expose the vein, the surgeon makes a series of incisions from the groin to the knee or the ankle leaving one or more skin bridges along the line of the incisions. (Some surgeons make one continuous incision from the groin to the knee or ankle). Handling of the vein must be kept to a minimum, but the vein must be removed from connective tissue that requires some force to remove. After exposing the vein, the surgeon grasps it with his fingers while stripping off the surrounding tissues with dissecting scissors or other scraping instruments. The surgeon uses his fingers and blunt dissection tools to pull and lift (or mobilize) the vein from the surrounding tissue. The vein is mobilized or pulled as far as possible through each incision. To reach under the skin bridges, the surgeon lifts the skin with retractors and digs the vein free. While stripping the vein, the surgeon will encounter the various tributary veins that feed into the saphenous vein. These tributaries must be ligated and divided. To divide and ligate tributaries that lie under the skin bridges, the surgeon may need to cut one end of the saphenous vein and pull it under the skin bridge to gently pull the vein out from under the skin bridge until the tributary is sufficiently exposed so that it may be ligated and divided. When the vein has been completely mobilized, the surgeon cuts the proximal and distal ends of the vein and removes the vein from the leg. After removal, the vein is prepared for implantation into the graft site, and the long incisions made in the leg are stitched closed.
The procedure described above can be used to harvest veins for a femoral popliteal bypass, in which an occluded femoral artery is bypassed from above the occlusion to the popliteal artery above or below the knee. The procedure can also be used to harvest veins for the revascularization of the superior mesenteric artery which supplies blood to the abdominal cavity and intestines. In this case, the harvested vein is inserted between the. aorta to the distal and patent (unblocked) section of the mesenteric artery. For bypass grafts of the lower popliteal branches in the calf, the procedure can be used to harvest the umbilical vein. The harvested vein can also be used for a vein loop in the arm (for dialysis) between the cephalic vein and brachial artery. The procedures may be used also to harvest veins for femoral-tibial, femora-peroneal, aorto-femoral, and iliac-femoral bypass operations and any other bypass operation.
As can be seen from the description of the harvesting operation, the harvesting operation is very traumatic in its own right. In the case of coronary artery bypass, this operation is carried out immediately before the open chest operation required to graft the harvested vein into the coronary arteries. The vein harvesting operation is often the most troublesome part of the operation. The long incisions created in the leg can be slow to heal and very painful. Complications resulting from the vein harvesting operation can also hinder the patient's recovery from the entire operation.
The method of vein harvesting presented herein is accomplished with endoscopic procedures. This allows the veins to be harvested in an operation that requires only a few small incisions. Endoscopic surgical techniques for operations such as gall bladder removal and hernia repair are now common. The surgeon performing the operation makes a few small incisions and inserts long tools, including forceps, scissors, and staplers into the incision and deep into the body. Viewing the tools through an endoscopic laparoscope, or a video display from the endoscope, the surgeon can perform all the cutting and suturing operations necessary for a wide variety of operations. The procedures are also referred to as laparoscopic surgery, minimally invasive surgery, or video-assisted surgery. References to endoscopic surgery and endoscopes below is intended to encompass all these fields, and all operations described below with reference to endoscopes can also be accomplished with laparoscopes, gastroscopes, and any other imaging devices which may be conveniently used.
Minimally invasive procedures for vein removal have been proposed. Knighton, Endoscope and Method for Vein Removal, U.S. Pat. No. 5,373,840 shows a method of cutting the saphenous vein at one end, and grasping the vein with graspers or forceps, then sliding a ring over the vein while holding it. Knighton uses a dissecting tool with an annular cutting ring, and requires that the saphenous vein be overrun or progressively surrounded with the dissecting tool and the endoscope, so that after the endoscope has been inserted as far as it will go, the entire dissected portion of the vein has been pulled in the lumen of the endoscope. As shown in FIGS. 1 and 10 of Knighton, the method requires deployment of the forceps inside the annular dissection loop, and it requires deployment of the loop and graspers inside the endoscope lumen. The blood vessel must be cut and grasped by the forceps before it can be dissected by the dissecting ring.
The method of vein harvesting presented below may use a balloon to assist in dissecting the harvested vein. An everted balloon stored inside a cannula or trocar may be inserted through one of the small incisions and inflated so that it everts out the end of the cannula and forces its way along the vein to create a tunnel. Endoscopic balloons have been used for retraction and dissecting in other applications, but not for dissection and tunneling for harvesting blood vessels. Kieturakis and Mollenauer, Apparatus and Method for Developing an Anatomic Space for Laparoscopic Procedures with Laparoscopic Implantations, U.S. Pat. No. 5,540,791 shows a balloon designed to separate the peritoneum from the overlying fascia (skin, fat, and connective tissue). This creates a working spare for laparoscopic repair of hernias: The balloons described below provide additional features making it suitable for use in endoscopic or laparoscopic vein harvesting.
It is an object of the inventions presented herein to provide methods and devices for harvesting veins with a less traumatic operation than the operations presently -used to harvest veins.